An anaphase calcium signal controls chromosome disjunction in early sea urchin embryos.
A transient increase in intracellular calcium concentration [Ca2+]i occurs throughout the cell as sea urchin embryos enter anaphase of the first cell cycle. The transient just precedes chromatid disjunction and spindle elongation. Microinjection of calcium chelators or heparin, an InsP3 receptor antagonist, blocks chromosome separation. Photorelease of calcium or InsP3 can reverse the block. Nuclear reformation is merely delayed by calcium antagonists at concentrations that block chromatid separation. Thus, the calcium signal triggers the separation of chromatids, while calcium-independent pathways can bring about the alterations in microtubule dynamics and nuclear events associated with anaphase progression. That calcium triggers chromosome disjunction alone is unexpected. It helps explain previous conflicting results and allows the prediction that calcium plays a similar role at anaphase in other cell types.
Groigno
L
L
Department of Physiological Sciences, University of Newcastle Upon Tyne Medical School, United Kingdom.
Whitaker
M
M
D000705:Anaphase / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D002842:Chromatids / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004625:Embryo, Nonmammalian; D006493:Heparin / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates / Q000502:physiology; D008870:Microtubules; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000502:physiology; D012617:Sea Urchins / Q000196:embryology; D015398:Signal Transduction / Q000502:physiology*; D008941:Spindle Apparatus / Q000502:physiology
D015220:Calcium Channels; D002614:Chelating Agents; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates; D018160:Receptors, Cytoplasmic and Nuclear; C053459:5,5'-dibromo-1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D004533:Egtazic Acid; D006493:Heparin; D002118:Calcium